The **M2UDS-20-R** is an industrial-grade **Two-Channel Digital Speed Switch** (also known as a Tachometer Relay) manufactured by **Nidec-Shimpo** (formerly Shimpo). It is designed to monitor rotational speed (RPM) and trigger specific electrical outputs when certain speed thresholds are met. --- ## 1. Core Technical Specifications | Feature | Specification | | :--- | :--- | | **Model Number** | M2UDS-20-R | | **Power Supply** | 85 – 264 VAC (Wide Range) | | **Input Signals** | Pulse (Open Collector, Contact, or Voltage Pulse) | | **Output Type** | Relay Contact (SPDT) | | **Number of Channels** | 2 (Independent Setpoints) | | **Display** | 5-Digit Red LED | | **Accuracy** | ±0.01% of displayed value | --- ## 2. Key Electronic Components & Functions ### A. The Microprocessor Unit (MPU) The heart of the device is a high-speed microprocessor that performs period measurement. Instead of counting pulses over a long duration, it measures the time between pulses to calculate instantaneous RPM with high precision. ### B. Input Signal Conditioning The input stage is versatile, allowing the device to interface with various sensors: * **Proximity Sensors:** Detects metal teeth on a gear. * **Rotary Encoders:** For high-resolution feedback. * **Magnetic Pickups:** Passive sensors that generate AC voltage. ### C. The Dual Relay System (Output) The "20" in the model name indicates dual setpoints. These are physical **Relays** that act as switches: 1. **Lower Limit (L):** Triggers if the speed falls below a set value (e.g., machine stall). 2. **Upper Limit (H):** Triggers if the speed exceeds a set value (e.g., overspeed protection). ### D. Analog-to-Digital / Digital-to-Analog While this specific model uses a digital display and relay output, it utilizes internal DACs to handle scaling and conversion of pulse frequencies into readable numeric data. --- ## 3. Practical Applications * **Conveyor Monitoring:** To stop the line if a motor burns out or a belt snaps (Under-speed). * **Engine Overspeed Protection:** To cut fuel or ignition if an engine exceeds its safe RPM limit. * **Flow Measurement:** When connected to a turbine flow meter, it acts as a flow rate monitor. --- ## 4. Typical Wiring Configuration ```text [ Power Supply ] ------> Terminals 1 & 2 (85-264VAC) [ Speed Sensor ] ------> Terminals 8, 9, 10 (Signal & Power) [ Relay Output 1] ----> Terminals 3, 4, 5 (Common, NC, NO) [ Relay Output 2] ----> Terminals 6, 7 (Common, NO/NC) ```